Photon-counting-type radiation detection under high dose (under high counting) condition such as X-ray computed tomography (CT) requires measurement to be performed by making a photoelectric conversion gain of a detector constant in order to accurately measure energy of radiated photons.
However, high counting of a light source of radiated photons has caused electric charges charged in a power supply node to be extracted along current output from a detector resulting from photon incidence, and a power supply voltage of the detector to vary.